Production of long chain alkyl substituted aromatic hydrocarbons



PRODUCTION 8F LONG CHAIN ALKYL SUB- STITUTED AROMATEC HYDROCARBGNS Robert A. Sanford, Park Forest, and Bernard S. Friedman, Chicago, Ill., assignors to Sinclair Refining Company, New York, N. Y., a corporation of Maine No Drawing. Application April 1, 1954, Serial No. 420,448

Claims. (Cl. 260-671) Our invention relates to the production of long chain alkyl substituted aromatic hydrocarbons which have particular value in the production of oxidation-stable alkyl aromatic acids and detergent compositions. More par ticularly, our invention relates to the production of such alkyl aromatics in which the alkyl group contains at least 8 carbon atoms by the alkylation of aromatic hydrocarbons with scission-susceptible olefins in the presence of hydrogen fluoride catalysts.

Long chain alkyl aromatic hydrocarbons are conventionally produced by the alkylation of an aromatic hydrocarbon, e. g. benzene, in the presence of an alkylation catalyst such as hydrogen fluoride. When the alkylation is carried out with a straight chain olefin, the olefin remains intact and the desired long chain alkyl aromatic hydrocarbon is produced with no difiiculty. Scissionsusceptible polyolefins, such as diisobutylene, may also be used to react with more reactive aromatic nuclei such as phenol to produce long chain alkyl aromatics. When, however, the scission-susceptible olefins are reacted with monocyclic aromatic hydrocarbons such as benzene and toluene, the olefin apparently undergoes extensive polymerization and depolymerization or cleavage prior to alkylation and the resulting product is a mixture of alkyl aromatic hydrocarbons containing new side chains both lower and higher in aliphatic molecular weight than the olefin originally used. This degradation of the olefin also results in the production of substantially inseparable polyalkylated aromatics of the same molecular Weight and boiling range as the desired alkyl aromatic. For example, when benzene is alkylated with diisobutylene under normal alkylation conditions, the olefin appears to undergo depolymerization prior to alkylation and the final product consists mainly of short chain monoand di-tertiary butylated benzene rather than long chain octylated benzene. This is very undesirable, as sulfonation of this mixture produces low yields of sulfonates which are poor in detergent quality and which require costly purification to eliminate or reduce odor, unsulfonated residue and color bodies. Because of this difiiculty, processes dealing with the production of long chain alkyl aromatics for detergent manufacture by the alkylation of aromatics with an olefin specify that the olefin be substantially free from scission-susceptible olefins such as isobutylene polymers or copolymers.

We have now found that valuable long chain alkyl substituted monocyclic aromatic hydrocarbons in which the alkyl group contains at least 8 carbon atoms are produced in good yields by the alkylation of the aromatic hydrocarbon with scission-susceptible olefins containing at least 8 carbon atoms in the presence of catalysts comprising hydrogen fiuoride by controlling the temperature between about 65 to 20 C. By controlling the temperature within the above range, cleavage of the olefins is avoided. Thus, toluene is octylated or dodecylated with diisobutylene or triisobutylene, respectively, or select cleavage-alkylation occurs resulting in the production of alkyl aromatics in which the alkyl group contains at least 2,810,770 Patented Oct. 22, 1957 2 8 carbon atoms, for example, octylation of toluene with tetraisobutylene. Undesirable cleavage resulting in the formation of short chain butylated products is substantially avoided and formation of undesirable short chain and polymer products is kept to a minimum.

According to the process of our invention, a monocyclic aromatic hydrocarbon is reacted with a scissionsusceptible olefin in the presence of a catalyst comprising hydrogen fluoride while controlling the temperature between about to -20 C. At higher temperatures, excessive butylation occurs and at lower temperatures excessive polymerization occurs with little intact alkylation. The reaction is stopped, for example, by quenching with water, the product washed with water or alkali solution, dried and the products recovered by distillation.

Generally, the catalyst and aromatic are mixed and contacted with the olefin. The manner of contacting is important in that abnormal orientation and cleavage may occur with alkylation products While the addition of the olefin to the catalyst and aromatic mixture is being completed. We have found that keeping the olefin concentration low during alkylation and keeping additional contact time after olefin addition to a minimum avoids abnormal orientation and cleavage reactions and results in the production of high yields of the desired alkyl aromatic. Thus, slow addition of the olefin and early quenching of the reaction is preferred procedure. Advantageonsly, two streams, one containing aromatic hydrocarbon and the olefin and the other aromatic hydrocarbon and catalyst, are directed into a mixing chamber and after a short contact time discharged into a stream of Water to stop the reaction. The molar ratio of aromatic to olefin to catalyst may vary from about 36:0.5-l.5:0.5-5. Preferably the ratio is about 5:1:1. The product is re covered by alkali washing and distillation.

By the process of our invention, readily available scission-susceptible olefins can be employed as the olefin source Without losses and complications previously encounterd in alkylati-on reactions with aromatic hydrocarbons because of cleavage reactions, to produce, selectively, valuable alkylated aromatics, some of which are novel compounds. The novel compounds produced by our invention are tertiary-alkylated saturated hydrocarbon substituted benzenes in which the tertiary-alkyl radical is of a particular type and contains at least 8 carbon atoms, particularly from S to 20 carbon atoms. The tertiaryalkyl radical of our novel compounds is a radical in which all methylene (CHz-) or methinyl groups are attached to at least two quaternary carbon atoms.

The novel compounds include, for example, tertiaryalkylated toluenes such as t-octyl-toluenes or paraor meta- (l,l,3,3 -tetramethylbut'yl) toluenes, t-dodecyltoluenes or 2,2,4,6,6-pentamethyl-4-(paraor meta-tolyl) heptanes; tertiary-alkylate-d dimethyl benzenes such as dimethyl-(t-octyl)-benzenes or 4- or 5- (l,1,3,3-tetramethylbutyl) -l,2- or 1,3- dimethylbenzenes; and tertiaryalkylated butyl benzenes such as 1-t-butyl-4-t-octylbenzone or p-(1,l,3,3-tetramethylbutyl)-t-butyl-benzene. By our invention not only one but two or more of long chain alkyl groups such as t-octyl, t-dodecyl and t-hexadecyl can be attached to aromatic hydrocarbons. Cleavage resulting in undesirable butylated products is kept to a minimum and a minimum of polymer is produced. Select cleavage-alkylation is obtained, for example, high yields of para-t-octyl-toluene are obtained from tetraisobutylene. Select polymerization-alkylation is obtained, for example, para-t-dodecyl-toluene is obtained from diuseful in the. production of oxidation-stable alkyl aromatic acids. Because of the resistance of the particular type of tertiary-alkyl substituent, tertiary-alkylated' saturated hydrocarbon substituted benzenes such as toluene or xylene can be oxidized selectively at the alkyl or cycloalkyl substituents to produce oxidation-stable tertiaryalkylated benzoic, phthalic or trimesic acids useful in greases and, when esterified, inrplasticizers and resins. The structure of the tertiary-alkyl group of our novel compounds provides'advantageous oxidation resistance in that all methylene or methinyl groups are attached to at least two quaternary carbon atoms. For example, the tertiary groups in the tertiary-octyl and tertiary-nonyl aromatics of our invention have the following structure:

and

t l CC O-aromatic Thus, the normally vulnerable position s in the methylene group of the tertiary-octyl radical and position ss in the methinyl group of the tertiary-nonyl radical are protected 7 by the adjacentquaternary groups which effectively pre- I o o and The aromatics are also useful, for example, in the electrical field where thermal and oxidation stability. re-

quirements are critical, for example, as transformer oils,

or as'a base for highly oxidation-resistant fluids, for examplefbrake-fluids, and grease lubricants or as plasticizers. Also, the aromatics provide hitherto unavailable alkylated aromatics for sulfonation to produce detergents, wetting agents and emulsifying agents, including synthetic oil-soluble sulfonates. In addition, nitration and reduction of these aromatics yield useful amines for surfactive agents and inhibitors.

By scission-susceptible olefins, we mean olefinscontaining at least 8 carbon atoms which tend to undergo cleavage. under normal alkylation conditions. 'The most useful .scission-susceptible olefins contain from 8.to carbon atoms. Examples of such olefins include polymers ,of isobutylene, for example, .diisobutylene, triisobutylene and tetraisobutylene, polymers of isoamylene, isohexylene and isoheptylene asiwellas co-polymers of isobutylene 'WithQpropylene, n-butyleneandamylene. Theease of alkylation without undesirable cleavage reactions varies. 75

with the molecular weight of the olefin. Thus, alkylation without undesirable cleavage is more diflicult with the higher molecular weight olefins than with 'diisobutylene, for example, but such alkylation can be eifected.

By monocyclic aromatic hydrocarbons, useful for alkylation according to the process of our invention, we mean benzene and saturated hydrocarbon substituted benzenes, i. e. alkyl and cycloalkyl substituted benzenes, preferablycontaining not more than 12 .carbon atoms in the alkyl or cycloalkyl group. For example, toluene,

butylbenzene, cyclohexylbenzene, octylbenzene, dimethyl-. benzene, (l methyl-cyclopentyl)benzene, cyclohexyl: toluene, octyltoluene, and (l-methyl-cyclopentyl)toluene are useful substituted benzenes. The ease of alkylation varies with the type of substitution present in the henzene ring, usually decreasing in reactivity, for example, in the following order; xylene, toluene, benzene, butylbenzene and octylbenzene.

By hydrogen fluoride .catalysts, we mean unpromoted hydrogen fluoride or hydrogen fluoride promotedrwith boron trifiuoride. Preferably, anhydrous hydrogen fluo ride is employed as less concentrated solutions of hydrogen fluoride promote the rate of undesirable polymerization at the expense of alkylation.

In the alkylation, the temperature required for'optimum alkylation withrminimum undesirable cleavage and polymer formation varies with the catalyst and the reactivity of the aromatic used. For example, optimum octylation of toluene occurs at about 50 to 30 C. whereas with benzene, a less reactive aromatic, optimum octylation occurs at about -35 to 25 C. The use of hydrogen fluoride promoted with boron trifluoride requires somewhat lower temperatures.

C. and of benzene atfabout ---50? C. In the alkyla- The process of our inventionwill' be further'illustrated by the following examples, 7 i 7 Example I A three necked stainless steel flask was fitted. with a stainless steel stirrer, a thermometer in a stainless steel thermowell and a reflux condenser. An isopropanol bath cooled with Dry Ice was used to obtain sub-zero temperatures. 75 grams of anhydrous hydrogen fluoride were added at 20 C. to 345 grams of toluene in the flask and to this stirred mixture were added 84 grams of diisobutyleneover a period of 50 minutes Stirring was continued for 60 minutes after addition of the olefin. The reaction temperature was maintained at -20 C. The reaction was stopped by quenching the hydrocarbon layer'with water. with water and sodium bicarbonate solution, dried over anhydrous potassium carbonate and fractionally distilled; The distilled products were examined with an infrared Example H Using the procedure of Example I, the same proportions of anhydrous hydrogen'fluoride, toluene and diiso butylenewere reacted. '11 e catalyst was added at 40 C. and the olefin was added over a period of 41 minutes and stirring was continued for 60 minutes. The reaction temperature was maintained at 40 C. I The products, based on the weight percent olefin converted, were 86.8

percent para-t-oct'yl and 5.2:percent"metai-octyl-tolueneand only 1.3 percent polymer. No butylation was ob-' For example, optimum octylation of toluene occurs at about to l The alkylation products were washedobsei ed. The high served. The high para-meta isomer ratio of t-octyltoluene shows select orientation.

Example III Using the procedure of Example I, 75 grams of anhydrous hydrogen fluoride were added at 60" C. to 345 grams of toluene. 84 grams of diisobutylene were added to the stirred mixture over a period of 30 minutes and stirring was continued for 60 minutes. The reaction temperature was maintained at 60 C. The products, based on the weight percent olefin converted, where 69.0 percent para-t-octyl and 3.2 percent meta-t-octyl-toluene, 3.9 percent C12 di-substituted-toluene and 10.4 percent polymer. No butylation was observed. The high para/meta isomer ratio of t-octyl-toluene shows select orientation.

Example IV Using the procedure of Example 1, 75 grams of anhydrous hydrogen fluoride were added at 40" C. to 345 grams of toluene. 168 grams of tetraisobutylene were added to the stirred mixture over a period of 70 minutes and stirring was continued for 20 minutes. The reaction temperature was maintained at 40 C. The products, based on the weight percent olefin converted, were 72.6 percent para-t-octyl and 3.8 percent meta-t-octyl-toluene, 9.4 percent t-dodecyl-toluene, or 2,2,4,6,6-pentamethyl-4-(p-tolyl) heptane, and only 4.2 percent t-butyltoluene. No polymer was formed. Thus, select cleavagealkylation of the C16 olefin produced high yields of t-octyl-toluenes.

Example V Using the procedure of Example I, 50 grams of anhydrous hydrogen fluoride were added at 35 C. to 117 grams of benzene. 34 grams of diisobutylene were added to the stirred mixture over a period of 30 minutes and stirring was continued for 60 minutes. The reaction temperature was maintained at 35" C. The products, based on the weight percent olefin converted, were 19.8 percent t-octyl-benzene, 5.9 percent di-t-butyl-benzene, 29.6 percent polymer and only 8.1 percent t-butyl-benzene.

Example VI Using the procedure of Example I, 50 grams of anhydrous hydrogen fluoride were added at 20 C. to 266 grams cf o-xylene. 56 grams of diisobutylene were added to the stirred mixture over a period of 60 minutes and stirring was continued for minutes. The reaction temperature was maintained at C. The products, based on the weight percent olefin converted, were 94.3 percent t-octyl-o-xylene, or 1,2-dimethy1-4-(t-octy1) benzene, and 1.3 percent isomeric octyl-o-xylene and only 3.0 percent t-butyl-o-xylene. No polymer was formed.

Example VII Using the procedure of Example I, 75 grams of anhydrous hydrogen fluoride and 7.5 grams of boron trifluoride were added at C. to 345 grams of toluene. 84 grams of diisobutylene were added to the stirred mixture over a period of 70 minutes and stirring was continred for 20 minutes. The reaction temperature was maintained at 60 C. The products, based on the weight percent olefin converted, were 45.5 percent parat-octyl, 11.4 percent meta-t-octyl and 22.4 percent isomeric octyl-toluene and only 12.1 percent t-butyl-toluene. No polymer was formed.

Example VIII Using the procedure of Example I, 40 grams of anhydrous hydrogen fluoride were added at 40 C. to 264 grams of t-butyl benzene. 74 grams of diisobutylene were added to the stirred mixture over a period of 50 minutes and stirring was continued for 30 minutes. The reaction temperature was maintained at -40" C. The products, based on the weight percent olefin converted, were 12.5 percent t-octyl-butylbenzene, or l-t-butyl-4-toctylbenzene, 4.0 percent isomeric octyl-butylbenzene and only 7.1 percent t-butyl-butylbenzene and 8.6 percent polymer.

We claim:

1. A process for the production of long chain tertiary alkyl substituted monocyclic aromatic hydrocarbons in which the long chain alkyl group contains from 8 to 20 carbon atoms, which comprises reacting a monocyclic aromatic hydrocarbon selected from the group consisting of benzene and short chain alkyl substituted benzenes in which the short chain alkyl group contains up to four carbon atoms with polymers of isobutylene containing from 8 to 20 carbon atoms in the presence of a catalyst comprising hydrogen fluoride while controlling the temperatureat about to 20 C.

2. The process of claim 1 in which the monocyclic aromatic hydrocarbon is toluene.

3. The process of claim 1 in which the catalyst is anhydrous hydrogen fluoride.

4. The process of claim 1 in which the catalyst is hydrogen fluoride promoted with boron trifluoride.

5. A process for the production of long chain tertiary alkyl substituted toluenes in which the alkyl group contains from 8 to 20 carbon atoms, which comprises reacting toluene with a polymer of isobutylene containing from 8 to 20 carbon atoms in the presence of anhydrous hydrogen fluoride while controlling the temperature at about 50 to 30" C.

References Cited in the file of this patent UNITED STATES PATENTS 2,072,153 Bruson Mar. 2, 1937 2,232,117 Kyrides Feb. 18, 1941 2,437,356 Hill Mar. 9, 1948 2,456,119 Friedman et a1 Dec. 14, 1948 2,477,383 Lewis July 26, 1949 2,673,224 Kennedy et a1. Mar. 24, 1954 2,768,985 Schlatter Oct. 30, 1956 

1. A PROCESS FOR THE PRODUCTION OF LONG CHAIN TERTIARY ALKYL SUBSTITUTED MONOCYCLIC AROMATIC HYDROCARBONS IN WHICH THE LONG CHAIN ALKYL GROUP CONTAINS FROM 8 TO 20 CARBON ATOMS, WHICH COMPRISES REACTING A MONOCYCLIC AROMATIC HYDROCARBON SELECTED FROM THE GROUP CONSISTING OF BENZENE AND SHORT CHAIN ALKYL SUBSTITUTED BENZENES IN WHICH THE SHORT CHAIN ALKYL GROUP CONTAINS UP TO FOUR CARBON ATOMS WITH POLYMERS OF ISOBUTYLENE CONTAINING FROM 8 TO 20 CARBON ATOMS IN THE PRESENCE OF A CATALYST COMPRISING HYDROGEN FLUORIDE WHILE CONTROLLING THE TEMPERATURE AT ABOUT -65 TO -20*C. 